The present technique relates generally to X-ray sources. In particular, the present disclosure relates to X-ray tube cathodes, such as those contained in X-ray tubes used in medical X-ray imaging.
In non-invasive imaging systems, X-ray tubes are used in both X-ray systems and computer tomography (CT) systems as a source of X-ray radiation. The radiation is emitted in response to control signals during inspection, examination or imaging sequences. Typically, the X-ray tube includes a cathode and an anode. An emitter within the cathode may emit a stream of electrons in response to heat resulting from an applied electrical current via the thermionic effect. The anode may include a target that is impacted by the stream of electrons. The target may, as a result, produce X-ray radiation and heat.
The radiation spans a subject of interest, such as a human patient, and a portion of the radiation impacts a detector or a photographic plate where the image data is collected. In some X-ray systems the photographic plate is then developed to produce an image which may be used by a radiologist or attending physician for diagnostic purposes. In digital X-ray systems a photo detector produces signals representative of the amount or intensity of radiation impacting discrete pixel regions of a detector surface. The signals may then be processed to generate an image that may be displayed for review. In CT systems a detector array, including a series of detector elements, produces similar signals through various positions as a gantry is displaced around a patient.
During operation of the X-ray tube, the amount and energy of X-rays that are emitted by the X-ray tube may be affected by the voltage applied between the anode and cathode within the X-ray tube. Additionally, an electrical current flowing through a thermionic emitter within the cathode may affect the amount of X-ray radiation produced by an X-ray tube. In a general sense, the applied voltage may affect the X-ray penetration through the subject while the current and exposure time may affect the contrast of a resulting X-ray image.